Composite materials are known, which comprise a complex matrix, based on cobalt, iron or nickel, enriched with chromium, and a reinforcing phase consisting of monocrystalline fibers or whiskers of transition metal monocarbides such as TaC, NbC, TiC, ZrC or HfC, it being possible for these whiskers to consist of only one of these monocarbides or of a mutual solid solution of two or three of these carbides.
Such materials, which are described in U.S. Pat. application Ser. No. 2,160 of Jan. 12, 1970 (replaced by Ser. No. 268,751, now U.S. Pat. No. 3,871,835) in the name of the present Assignee, possess outstanding properties, and especially great mechanical strength, are devoid of both tensile fragility and impact fragility, and possess excellent resistance to oxidation and to corrosion at high temperatures, and resistance to creep and to fatigue under hot conditions which is greater than that of the best superalloys previously known.
In the patent application mentioned above, it was proposed to increase the hardness of the matrix by providing a component which, during a heat treatment of the material, first enters into solid solution and then afterwards leads to a precipitation which hardens the latter. However, this measure can only be applied to matrices based on nickel, the presence of a certain proportion of aluminum or of aluminum and titanium, making it possible to form a coherent .gamma.' phase, Ni.sub.or Ni.sub.3 (Al,Ti), which precipitates. In a matrix based on cobalt or iron, the precipitation is not stable at the temperatures contemplated for using the material.